Orientation info from HEIC decoder does not match actual pixel orientation

[rudchenkos]

Description

It turns out that in HEIC the pixels are never rotated and the metadata only indicates the orientation of the sensor when the photo was taken. After ReadHEICImage populates EXIF profile and returns a decoded image, the exif:Orientation property is interpreted by ReadImage which sets Image->orientation accordingly.

Hence, there is a discrepancy between Image->orientation and actual pixel orientation in images loaded with the heic coder. Particularly, this leads to incorrect behavior of the -auto-orient which in this case tries to compensate non-existing pixel rotation.

Steps to Reproduce

1. Take a HEIC image with exif:Orientation not equal to "1" (TopLeftOrientation). For instance, a portrait photo with one of the newer Apple iPhone devices. You can download an example photo here: https://www.dropbox.com/s/celi7ejhit9ybzb/test.heic?dl=0
2. Desktop image viewers like Preview on macOS normally display the photo as if camera was not rotated.
3. convert test.heic -auto-orient test.jpg

Expected result

test.jpg appears in viewers the same way as original.

Actual result

test.jpg appears sideways.

System Configuration

• ImageMagick version: 7.0.8-9 Q16
• Environment: macOS 10.13.6, but the problem is cross-platform